Does the flu shot prevent the flu?

Yes: The flu shot can be effective in prevention of whatever strains of influenza virus are covered the influenza combination used for that particular year. Even if one still catches the flu it is likely to be less aggressive.

Sometimes,however...: Manufacturers have to predict which strains will circulate each year. This year's vaccine is thought to be only 10% effective. Even in the best years it doesn't always work. Flu vaccine temporarily reduces immunity and can have serious side effects. If you get it only get the single-dose vial form rather than the more commonly used multi-dose which has more mercury. See http://tinyurl.com/y8bufvlr